(a) Field of the Invention
The present invention relates to a magnetic head capable of performing both recording and playback, and more particularly it pertains to a magnetic head assembly having vertically stacked separate units of recording and playback cores combined in a single head.
(B) Description of the Prior Art
As the arrangement of magnetic heads of a tape recorder, a three-head system comprising an erasing head, recording head and a playback head, which are independent of each other, is known. In such three-head system, each magnetic head is designed to behave under the optimum condition required for fulfilling its function.
The respective optimum conditions for the functions of recording head and playback head will be described hereunder. As the recording magnetic head, it is desirable generally that its core has a relatively wide gap at the front ends of the core which contact a running magnetic tape, and that it has such magnetic characteristics represented by a great density of its maximum magnetic flux and also by a low impedance. As the playback magnetic head, it is desirable generally that its core has a relatively narrow gap at the front ends of core and that it has a high impedance.
A further detailed description of these magnetic heads will be made by referring to FIGS. 1 and 2. FIG. 1 shows a frequency-playback output characteristic of a playback magnetic head, on the basis of the width of gap of the core serving as the parameter. FIG. 2 shows a gap width-recording efficiency characteristic of the core gap of the recording magnetic head. In FIG. 1, the arrow indicates the direction in which the core gap which serves as the parameter becomes narrower. The width of the gap is shown to become wider in the order of the symbols a, b and c. For the convenience of understanding, the properties which are required of a recording magnetic head may be summarized as follows:
(1) good recording efficiency; PA1 (2) good linearity of input and output characteristic; PA1 (3) large dynamic range; and PA1 (4) small distortion. PA1 (1) good frequency characteristic (minimized loss in high frequency range); and PA1 (2) good S/N ratio (high level of reproducing output).
Accordingly, a recording magnetic head whose core has an appropriately broad gap width as shown in FIG. 2 will provide the aforesaid properties.
The properties required of a playback magnetic head, on the other hand, may be summarised as follows:
Accordingly, as will be understood from FIG. 1, a playback magnetic head assembly having a narrower core gap is capable of satisfying the above-mentioned requirements.
As discussed above, it should be understood that, in a three-head system tape recorder, it is possible to design the respective magnetic heads so as to have their own optimum functions to satisfy their own assignments. This may be possible with an open-reel type recording and playback apparatus. However, would this be also possible with a tape recorder using a magnetic tape housed in a cassette?
A so-called cassette half is manufactured in strict conformity with a predetermined specifications allowing only small openings for receiving magnetic heads. For this reason, difficulty has been well recognized in attempting to make a three-head system for a cassette type tape recorder. As a result, it has been the usual practice to use a two-head system in a tape recorder, which comprises an erasing magnetic head and another magnetic head which concurrently has both the recording function and playback function.
Nevertheless, there is provided a three-head system cassette tape recorder which is arranged so that a third magnetic head assigned for playback or for recording is inserted in a small window other than those windows of a cassette half which are intended for the insertion of a recording magnetic head and playback magnetic head. However, from the structural point of view, this third magnetic head inevitably is required to be small, compact in size. Thus, according to the prior technique, there has not been obtained a fully satisfactory functional characteristic from such abnormally small-sized magnetic head as compared with a normal-sized such head. Furthermore, a magnetic head which is capable of satisfying the above-mentioned requirements of functions naturally has too complicated arrangement to be formed into such small size. Therefore, it has been extremely difficult to manufacture such a small-sized magnetic head having a satisfactory function. Furthermore, such a magnetic head gives rise to a problem in term of mechanical strength. What is more, the production of such magnetic head will unavoidably become expensive. For these reasons, the three-head system for cassette tape recorder has not reached the state of becoming popular. In addition, it is needless to say that a three-head system is more expensive as compared with the two-head system.
As one of recent models of the so-called three-head recording and playback combination systems, there is the arrangement that the recording magnetic head and the playback magnetic head are designed to exert their functions independently of each other and that these two magnetic heads are combined in horizontally adjacent relationship in the direction of the travel of the magnetic tape and also that the cores in the respective magnetic heads are aligned on the same horizontal lines. Such known horizontally arranged three-head system has the following inconveniences.
(a) It is difficult to insure the contact of a running magnetic tape onto the spaced core gaps under the same conditions, and accordingly the touch of the magnetic tape becomes unstable;
(b) The respective core gaps of the horizontally combined recording and playback magnetic head which may be called a double-gap type are desirably in contact, through a magnetic tape, with the urging pad whose size is standardized and which is housed within the cassette. Such arrangement inevitably calls for a drastic reduction in size of each of these two combined magnetic heads. This reduction in size, in turn, will lead to the previously mentioned deterioration of function and also to the difficulty in the manufacture of such a small-sized combination head; and
(c) The total area of contact between the magnetic tape and the contact surface of the magnetic head increases, resulting in an increase in the running resistance of the magnetic tape, i.e., an increase in the load of a tape pinch-roller and like member.